<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot></slot>
    </div>
    <div class="dots">
      <span class="dot" v-for="(item, index) in dots" :key="index" :class="{active: currentPageIndex===index}"></span>
    </div>
  </div>
</template>

<script>
import { addClass } from 'util/dom.js'
import BScroll from 'better-scroll'
export default {
  data() {
    return {
      dots: [],
      currentPageIndex: 0
    }
  },
  props: {
    // 循环轮播
    loop: {
      type: Boolean,
      default: true
    },
    // 自动轮播
    autoPlay: {
      type: Boolean,
      default: true
    },
    // 延时
    interval: {
      type: Number,
      default: 4000
    }
  },
  mounted() {
    setTimeout(() => {
      this._setSliderWidth()
      this._initDocts()
      this._initSlider()
      // 判断是否自动滚动
      if (this.autoPlay) {
        this._play()
      }
    }, 20)
    // 窗口改变事件
    window.addEventListener('resize', () => {
      if (!this.slider) {
        return
      }
      this._setSliderWidth(true)
      // 重新刷新
      console.log('refresh')
      this.slider.refresh()
    })
  },
  methods: {
    // 设置滚动宽度
    _setSliderWidth(resize) {
      this.children = this.$refs.sliderGroup.children
      let width = 0
      let sliderWidth = this.$refs.slider.clientWidth
      for (let i = 0; i < this.children.length; i++) {
        let child = this.children[i]
        addClass(child, 'slider-item')
        child.style.width = sliderWidth + 'px'
        width += sliderWidth
      }
      // 循环，并且不是 resize 改变,宽度增加两倍
      if (this.loop && !resize) {
        width += 2 * sliderWidth
      }
      this.$refs.sliderGroup.style.width = width + 'px'
    },
    // 初始化 slider
    _initSlider() {
      this.slider = new BScroll(this.$refs.slider, {
        scrollX: true,
        scrollY: false,
        momentum: false,
        snap: {
          loop: this.loop,
          threshold: this.threshold,
          speed: this.speed
        }
      })
      // 绑定滚动事件
      this.slider.on('scrollEnd', this._scrollEnd)
    },
    // 设置 docts
    _initDocts() {
      this.dots = new Array(this.children.length)
    },
    // 滑动事件
    _scrollEnd() {
      let pageIndex = this.slider.getCurrentPage().pageX
      if (this.autoPlay) {
        this._play()
      }
      if (this.loop) {
        pageIndex -= 1
      }
      this.currentPageIndex = pageIndex + 1
    },
    // 设置自动播放
    _play() {
      clearTimeout(this.timer)
      let pageIndex = this.slider.getCurrentPage().pageX
      this.timer = setTimeout(() => {
        this.slider.next()
        this.currentPageIndex = pageIndex + 1
      }, this.interval)
    }
  },
  destroyed() {
    clearTimeout(this.timer)
  }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import '../../assets/stylus/variable.styl';

.slider {
  // height: 1px;
  position: relative;

  .slider-group {
    position: relative;
    overflow: hidden;
    white-space: nowrap;

    .slider-item {
      float: left;
      box-sizing: border-box;
      overflow: hidden;
      text-align: center;

      a {
        display: block;
        width: 100%;
        overflow: hidden;
        text-decoration: none;
      }

      img {
        display: block;
        width: 100%;
      }
    }
  }

  .dots {
    position: absolute;
    right: 0;
    left: 0;
    bottom: 12px;
    text-align: center;
    font-size: 0;
    z-index: 99;

    .dot {
      display: inline-block;
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background-color: #fff;
      margin: 0 4px;
      background: $color-text-l;

      &.active {
        width: 20px;
        border-radius: 5px;
        background: $color-text-ll;
      }
    }
  }
}
</style>